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1.
The purpose of this study was to evaluate the cytochrome P450-dependent monooxygenase activities in methidathion resistant and susceptible strains of Amblyseius womersleyi Schicha. Artificial laboratory selections for resistance and susceptibility to methidathion were performed in an organophosphate resistant strain of A. womersleyi (Kanaya strain). Selections for susceptibility were also performed in a susceptible strain of this predaceous mite (Ishigaki Strain). After the selection process, the LC50 of methidathion for the selected strains of A. womersleyi were 816 mg/l (Kanaya R), 4.61 mg/l (Kanaya S) and 1.59 mg/l (Ishigaki S). The monooxygenase activities were determined biochemically by the O-deethylation of 7-ethoxycoumarin (7-EC). The monooxygenase activity in adult females of Kanaya R strain (51.1 pmol/30 min/mg protein) was 3.60- and 5.42-fold higher than the activity observed for Kanaya S and Ishigaki S strains, respectively. Significant correlation between monooxygenase activity and LC50 (mg/l) of methidathion was observed analyzing 16 populations of A. womersleyi with different susceptibilities to methidathion. Monooxygenase activity was also evaluated in different life stages (egg, larva, protonymph, deutonymph and adult) of A. womersleyi. The lowest activity was observed for the larval stage, which presented the highest susceptibility to methidathion. Protonymph, deutonymph and adult presented the highest monooxygenase activities. These stages were the most tolerant to methidathion. Monooxygenase activities of the Kanaya R strain were higher than of the Kanaya S strain in all developmental stages. The present study can be helpful for the implementation of a program involving release of insecticide-resistant populations of A. womersleyi in the field. The monooxygenase activity determination is easier and quicker than the estimation of LC50, requiring fewer mites.  相似文献   

2.
Banks grass mite, Oligonychus pratensis (Banks), from three Texas maize fields were assayed for bifenthrin resistance following poor field control in 1995. Laboratory bioassays showed the field mites to be 3- to 23-fold more tolerant to bifenthrin than the susceptible laboratory culture. Comparison of LC50 values to assays with bifenthrin from 1985 to 1993 indicated no statistically significant changes in mite resistance. However, high LC90 values in 1995 suggest possible resistance development. The percentages of resistant mites from the three fields in 1995 were calculated to be 4.7%, 17.9%, and 30.9%. The Banks grass mite population exhibiting the highest level of tolerance to bifenthrin was further assayed to evaluate tolerance levels to other insecticides alone and in combination with synergists and insecticides. A high level of tolerance existed in the 1995 ‘bifenthrin–selected’ Banks grass mite strain to bifenthrin, dimeothate, and amitraz. The combination of bifenthrin or dimethoate with a synergist indicated changes in the ability of the more resistant 1995 mites to detoxify insecticides. The activity of a dimethoate + bifenthrin mixture and a three way mixture of dimethoate, bifenthrin, and piperonyl butoxide caused 5- and 38-fold increase in toxicity against the more resistant Banks grass mite. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC50 value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC50 values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.  相似文献   

4.
Ten essential oils were tested against the cabbage looper, Trichoplusia ni larvae for contact, residual and fumigant toxicities and feeding deterrent effects. Against third instar T. ni, Syzygium aromaticum (LD50 = 47.8 μg/larva), Thymus vulgaris (LD50 = 52.0 μg/larva) (the two positive controls) and Cinnamomum glanduliferum (LD50 = 76.0 μg/larva) were the most toxic via topical application. Litsea pungens (LD50 = 87.1 μg/larva), Ilex purpurea (LD50 = 94.0 μg/larva), Cinnamomum cassia (LD50 = 101.5 μg/larva) and Litsea cubeba (LD50 = 112.4 μg/larva) oils were equitoxic. Thymus vulgaris (LC50 = 4.8 mg/ml) and S. aromaticum (LC50 = 6.0 mg/ml) oils were the most toxic in residual bioassays. Cymbopogon citratus (LC50 = 7.7 mg/ml) and C. cassia (LC50 = 8.5 mg/ml) oils were equitoxic followed by Cymbopogon nardus (LC50 = 10.1 mg/ml) in this bioassay. The remaining five oils showed little or no residual effects. In a fumigation bioassay, L. cubeba (LC50 = 16.5 μl/l) and I. purpurea (LC50 = 22.2 μl/l) oils were the most toxic. Cinnamomum glanduliferum (LC50 = 29.7 μl/l) and Sabina vulgaris (LC50 = 31.2 μl/l) oils were equitoxic. Interestingly, S. aromaticum did not exhibit any fumigant toxicity. Cymbopogon citratus, C. nardus and C. cassia strongly deterred feeding by third instar T. ni (DC50s = 26.9, 33.8 and 39.6 μg/cm2, respectively) in a leaf disc choice bioassay. The different responses of T. ni larvae to the oils in different bioassays suggest that these essential oils exhibit different modes of action. Based on their comparable efficacy with essential oils already used as active ingredients in many commercial insecticides (i.e. clove oil and thyme oil), some of these essential oils may have potential as botanical insecticides against T. ni.  相似文献   

5.
Permethrin resistance status of a laboratory strain, a permethrin-selected strain and three field strains of Aedes aegypti collected in Kuala Lumpur, Malaysia were evaluated using three standard laboratory bioassays: WHO larval bioassay, WHO adult mosquito bioassay, and mixed function oxidase (MFO) enzyme microassay. The LC50 values of field strains from the WHO larval bioassay did not differ significantly. The highest LC50 value was from the Taman Melati field strain (0.39 mg/L). The resistance ratio for the permethrin-selected strain and the field strains ranged from 1.86 fold to 5.57 fold. Pre-exposure to piperonyl butoxide (PBO) in the WHO adult bioassay and MFOs enzyme microassay reduced the LT50 values and reduced the mean optical density of elevated oxidase activity (0.28–0.42) at 630 nm. The LC50 or LT50 values and the level of oxidases were significantly correlated (r = 0.825; p< 0.05). This study confirmed the presence of permethrin resistance in these mosquito populations.  相似文献   

6.
Using susceptible and resistant reference strains and standard bioassay methods a new miticide product was screened for efficacy and cross-resistance against two-spotted spider mite, Tetranychus urticae Koch. Experimental product NN1 850.0 EW (fenpyroximate and propargite 3:10 ratio) was significantly (P<0.05) more toxic than either compound tested alone (co-toxicity index 1029). Non-overlapping 95% CIs at the LC50 and LC99 level suggest that there is no cross-resistance to NN1 850.0 EW from existing organophosphate and pyrethroid resistance. NN1 850.0 EW is worthy of further development for T. urticae control.  相似文献   

7.
Abstract

Dimethoate is one of the organophosphate insecticides widely used in agriculture throughout the world and is an inhibitor of cholinesterase in animals. The objective of the present study was to detect oxidative stress and DNA damage induced by dimethoate in the freshwater fish Channa punctatus (C. punctatus). The LC50-96 h value of technical grade dimethoate was estimated at 19.10 μg L-1 in a semi-static system and, on the basis of the LC50 value, three concentrations were determined. The fish were exposed to these concentrations of dimethoate for 96 h and samplings were done at 24 and 96 h for assessment of oxidative stress and DNA damage. After exposure to dimethoate, the level of superoxide dismutase declined while lipid peroxidation, glutathione, induction of micronucleus and DNA damage were increased in C. punctatus as the concentration and exposure time increased. Thus our results suggest that dimethoate induces genotoxic effects which invariably accompanied and correlated with oxidative stress.  相似文献   

8.
Persea mite, Oligonychus perseae Tuttle, Baker, and Abatiello, susceptibility to abamectin and milbemectin was evaluated in 2003 to determine baseline susceptibility levels in avocado groves in San Diego and Ventura Counties (California, USA) where more than 70% of the state’s avocado production is concentrated. Milbemectin has yet to be used in avocado production in California and abamectin has been available for use since 1999. Baseline susceptibility ratios (in relation to the most susceptible population) of five persea mite field strains to milbemectin varied 2.1- to 2.8-fold at the LC50 and LC90, respectively. The susceptibility of seven field strains to abamectin varied slightly more (2.1- to 3.5-fold) with one strain subjected to seven sprays over the past 4 years showing slight but significant separation of LC50 and LC90’s from the most susceptible strain, which is suggestive of the early stages of resistance to this product. Based on these data, baseline susceptibility levels are proposed that might be used to monitor for future persea mite resistance to these chemicals as their use in California avocado production continues.  相似文献   

9.
Considering the rapid transmission of the dengue virus, substantial efforts need to be conducted to ward-off the epidemics of dengue viruses. The control effort is depending on chemical insecticides and had aroused undesirable conflicts of insecticide resistance. Here, we study the entomopathogenic fungus, Metarhizium anisopliae as a promising new biological control agent for vector control. The pathogenicity effects of Metarhizium anisopliae against field and laboratory strains of Aedes albopictus and Aedes aegypti larvae were tested using the larvicidal bioassay technique. The results demonstrate that the treatments using M. anisopliae isolate MET-GRA4 were highly effective and able to kill 100% of both Ae. albopictus and Ae. aegypti mosquito larvae at a conidia concentration of 1 × 10?/ml within 7 days of the treatment period. The fungus displayed high larvicidal activity against laboratory and field strain of Ae. aegypti larvae with LC50 values (9.6 × 103/ml, 1.3 × 103/ml) and LC95 values (1.2 × 10?/ml, 5.5 × 105/ml) respectively. For Ae. albopictus, LC50 values for laboratory and field strains were (1.7 × 104/ml, 2.7 × 104/ml) and the LC95 values were (2.1 × 10?/ml, 7.0 × 105/ml) respectively. Interestingly, the susceptibility of field strain towards M. anisopliae was higher as compared to the laboratory strain Aedes larvae. In which, the causative agents of all the dead larvae were verified by the virulence of M. anisopliae and caused morphological deformities on larval body. The findings from this study identify this isolate could be an effective potential biocontrol agent for vector mosquitoes in Malaysia.  相似文献   

10.
Nine Washington populations ofTyphlodromus (=Metaseiulus) occidentalis Nesbitt collected from commercial apple orchards were surveyed for resistance to ten pesticides. A susceptible population collected from wild blackberry which had no history of pesticide exposure was used in estimating resistance development. All populations from apple orchards were tolerant to high concentrations of azinphosmethyl, diazinon, endosulfan and propargite. Resistance was also apparent to these materials, especially for azinphosmethyl which produced over 100-fold resistance levels for several populations. Moderate to low levels of tolerance and resistance development were seen to field concentrations of cyhexatin, formetanate and carbaryl. Fenvalerate, methomyl and methidathion were all very toxic at field concentrations and little evidence of resistance development was apparent. The use of fenvalerate, methomyl or methidathion at a time whenT. occidentalis is active would likely abrogate favorable biological control of pestiferous orchard mites.Scientific Paper No. 7502  相似文献   

11.
Cells ofPityrosporum ovale that colonize human pilosebaceous units are constantly exposed to cutaneous androgenic steroids. The aim of our study was to find out whetherP. ovale is susceptible to these hormones. Three strains ofP. ovale were grown in vitro in the presence of various concentrations oftestosterone, dehydroepiandrosterone, androstenedione, androstanedione, 5--dihydrotestosterone andprogesterone (10, 100, and 1000 µg/ml; agar dilution assays). In addition, three strains ofCandida albicans were also exposed to equal concentrations of the same androgens. As a result, allP. ovale strains were suppressed by 1000 µg/mlandrostenedione, which was the strongest inhibitor. The other androgenic steroids also significantly reducedP. ovale growth at different concentrations, depending on the hormone used and the strain tested.Progesterone was inhibitory at the highest concentration for oneP. ovale strain only.Candida albicans was not affected by any of the androgens. These findings demonstrate an in vitro susceptibility ofP. ovale to high concentrations of human androgenic steroids. A relevance of this interaction for the in vivo fungus-host relation is not apparent.  相似文献   

12.
Kucey  R. M. N.  Snitwongse  P.  Chaiwanakupt  P.  Wadisirisuk  P.  Siripaibool  C.  Arayangkool  T.  Boonkerd  N.  Rennie  R. J. 《Plant and Soil》1988,108(1):33-41
Controlled environment and field studies were conducted to determine relationships between various measurements of N2 fixation using soybeans and to use these measures to evaluate a number ofBradyrhizobium japonicum strains for effectiveness in N2 fixation in Thai soils.15N dilution measurements of N2 fixation showed levels of fixation ranging from 32 to 161 kg N ha−1 depending on bacterial strain, host cultivar and location. Midseason measures of N2 fixation were correlated with each other, but not related measures taken at maturity. Ranking ofB. japonicum strains based on performance under controlled conditions in N-free media were highly correlated with rankings based on soybean seed yields and N2 fixation under field conditions. This study showed that inoculation of soybeans with effectiveB. japonicum strains can result in significant increases in yield and uptake of N through fixation. The most effective strains tested for use in Thai conditions were those isolated from Thai soils; however, effective strains from other locations were also of benefit.  相似文献   

13.
Yu J  Pang Y  Tang M  Xie R  Tan L  Zeng S  Yuan M  Liu J 《Current microbiology》2001,43(2):112-119
The chromosome of the Bacillus thuringiensis strain S184 that was toxic against the third instar larvae of Spodoptera litura with the LC50 of 9.74 μg/ml was successfully integrated into two genes of cyt1Aa and cry11Aa using the transposon Tn917, yielding the primary engineered strain TnX. The strain TnX was highly toxic to the third instar larvae of Culex pipiens fatigans with the LC50 of 5.12 ng/ml which was 1.82-fold higher than that of B. thuringiensis subsp. israelensis, but lowly toxic to lepidopterous larvae. By the protoplast fusion of the strain TnX and the strain S184-Tetr (resistance to tetracycline), the target engineered strain TnY was obtained. Against the third instar larvae of S. litura, the strain TnY LC50 was of 4.68 μ g/ml and increased by 2.08-fold in comparison with the parent strain S184. Against the third instar larvae of C. pipiens fatigans, the strain TnY LC50 was of 103.20 ng/ml. The two target genes of cyt1Aa and cry11Aa integrated into the chromosome were extremely stable and had little possibility of a second transposition. It was unclear whether some factors existing in the parent strain, S184, contributed to the high toxicity of the strains TnX and TnY. Received: 30 November 2000 / Accepted: 10 January 2001  相似文献   

14.
Production of a blue pigment, indigoidine, is a variable trait among wild-type strains ofErwinia chrysanthemi; it is also influenced by the composition of the growth medium. Starting with a nonpigmented wild-type strain (ICPB EC183) ofE. chrysanthemi, we obtained by nitrosoguanidine mutagenesis a pigmented (idg +) mutant strain (AC6055), which simultaneously was Arg. Linkage betweenarg andidg was established in two-factor transductional and conjugational crosses. Coinheritance ofidg withhis +,ilv +,leu +,ser +,thr +, orura + transductants was not observed. Spontaneous Arg+ revertants of AC6055 were invariably Idg+. The pigments produced by AC6055, Idg+ recombinants, and wild-type Idg+ strains were identical, judged by absorption spectra (max = 615 nm) of the dimethylsulfoxide extracts of whole cells. We concluded that nitrosoguanidine caused comutation in thearg andidg loci that are linked on theE. chrysanthemi chromosome.  相似文献   

15.
Ethanol tolerance, alcohol dehydrogenase (ADH;EC1.1.1.1) activity, and tissue-specific expression wereexamined in species of the cardini group ofDrosophila using D. melanogaster as astandard of comparison. In contrast to most fruit-breeding species, allcardini species examined, two from the cardini subgroupand five from the dunni subgroup, were ethanol sensitive(LC50 2.05%) and the mean ADH activityof males ranges from only 8 to 16% that of D.melanogaster AdhFF. Among all sevencardini species, there were small but significantdifferences in ethanol tolerance and ADH activity.Differences in enzyme mobility were in accordance with the proposedphylogeny for the dunni-subgroup species. ADH isexpressed in the fat body and midgut. Males of D.acutilabella and of D. belladunni havesignificantly less ethanol tolerance and express less ADH activitythan females in zymograms and histologicalpreparations.  相似文献   

16.
Acetylene-reducing activities (ARA) of strains ofEnterobacter agglomerans, Azospirillum brasilense, Azotobacter chroococcum, and Bacillus, isolated from temperate or tropical soils, were compared at different temperatures to study temperature adaptability. All Enterobacter strains and Bacillus strain C-11-25 reduced C2H2 at temperatures as low as 5°C. ARA by Enterobacter strains declined sharply above 30°C but ARA by Bacillus strain C-11-25 continued to increase with an increase in temperature.A. brasilense strain sp 245, isolated from wheat roots in Brazil, reduced more C2H2 at lower temperatures than strain Cd, isolated from a Californian soil. Similarly, the temperate strain ofA. chroococcum was a better N2 fixer than the tropicalA. chroococcum strain at lower temperatures. Tropical strains ofA. brasilense andA. chroococcum reduced more C2H2 than temperate strains at higher temperatures. Therefore, it appears that temperate and tropical N2-fixing organisms adapt themselves to their particular environment and should have more potential to benefit crops grown at the particular temperatures favorable to them. Only Bacillus strain C-11-25 has potential to benefit both temperate and tropical crops because it reduced significant acetylene over a wide temperature range.  相似文献   

17.
In this study, we formulated pesticides from 12 products, namely machine oil EC, imidacloprid WP, thiamethoxam WP, acetamiprid WP, methidathion EC, acequinocyl WP, clothianidin WP, deltamethrin EC, mancozeb WP, benomyl WP, difenoconazole WP, and bitertanol WP. These 12 pesticides were selected to determine their toxicity to green lacewing, Chrysoperla nipponensis, at the maximum field recommended dosage under laboratory conditions. Machine oil EC had extremely detrimental effects on eggs of C. nipponensis, resulting in 99% mortality (categorized as Class IV) when eggs were treated with machine oil EC by dipping. Mean larval corrected mortalities (%) for methidathion EC and deltamethrin EC were 62.5% (categorized as Class II) and 87.5% (categorized as Class III) respectively, when larvae were topically treated. As a result of dipping treatments of pupae with pesticides, machine oil EC and thiamethoxam WP were classified as slightly harmful (categorized as Class II). Methidathion EC showed high toxicity, resulting in a total effect index rate 100% (categorized as Class IV). Taxonomical notes of the genus Chrysoperla and C. nipponensis are reviewed here.  相似文献   

18.
Spodoptera litura is one of the most destructive polyphagous insect pests, with more than 120 host‐plant species. In our present study, a field‐collected population of S. litura when selected with spinosad for 11 consecutive generations resulted in the development of 3921‐fold resistance to spinosad as compared to the susceptible strain. The spinosad‐resistant strain of S. litura had a relatively high fitness cost (0.17) as compared to the susceptible strain. Furthermore, the lethal and sub‐lethal effects of different concentrations of spinosad were checked on the susceptible strain at different levels; i.e., LC40, LC30, LC20 and LC10, which revealed that the impact of spinosad on the life‐history traits of S. litura increased with the increase in concentration of spinosad. A significant impact of spinosad was recorded on the larval duration, pre‐pupal weight, pupal duration, pupal weight, reproductive potential and adult emergence. The outcomes of the current research clearly indicate that fitness cost of spinosad and its sub‐lethal effects have a significant impact on population dynamics of S. litura, for which it can be incorporated in integrated pest management.  相似文献   

19.
Twenty-nineFusarium species isolated from various sources in different districts of Taiwan were tested for their ability to produce fumonisins in corn cultures. OnlyFusarium moniliforme produced fumonisin B1 (FB1) and fumonisin B2 (FB2). The finding that the other 28Fusarium species produced neither FB1 nor FB2 is preliminary because only one strain per species was studied. The detection of FB1 and FB2 in cultures ofF. moniliforme was demonstrated by TLC and HPLC, and FB1 was further confirmed by mass spectrometry. In a separate experiment, in which 38 strains ofF. moniliforme were tested for fumonisins, approximately 66% (25/38) produced FB1 and/or FB2. Of the 25 strains, 14 produced only FB1 and 11 produced both FB1 and FB2, and the amounts of FB1 and FB2 produced by different strains varied greatly. This is the first report that fumonisins are found in corn cultures experimentally infected withF. moniliforme strains from Taiwan. It is safe to assume that fumonisin producing strains ofF. moniliforme are widely distributed among the economic crops such as corn, rice, sugarcane, and sorghum throughout the Island.Abbreviations FB1 Fumonisin B1 - FB2 Fumonisin B2 - OPA o-phthalidialdehyde  相似文献   

20.
Susceptibility of adults and puparia ofSturmiopsis inferens Tns. [Tachinidae, Diptera] to 9 commonly recommended insecticide sprays against sugarcane pests was determined. The chemicals tested as emulsifiable concentrates include lindane 0.1%, endosulfan 0.1%, monocrotophos 0.05%, quinalphos 0.05%, malathion 0.1%, dimethoate 0.1%, cypermethrin 0.01%, fenvalerate 0.01% and decamethrin 0.0014%. Lindane, malathion, dimethoate monocrotophos and quinalphos were highly toxic, while decamethrin had little harmful effect to the adults when exposed for 6 h to filter paper impregnated or sugarcane shoot bits sprayed with the chemicals. However, the insecticides had no harmful effect on the puparia and adult emergence was normal from the puparia sprayed with insecticides. In another study, susceptibility of adults to soil application of lindane EC, carbofuran G, chlorpyriphos G, Sevidol G and whorl application of lindane G, chlorpyriphos G and Sevidol G was tested in pot culture. Except for soil application of lindane EC, all other chemicals had no harmful effect to the adults in pot culture experiment. In a field trial, commonly recommended insecticides against shoot borer,Chilo infuscatellus Snell.viz., soil application of granules of lindane, carbofuran, chlorpyriphos and Sevidol and folia spray of endosulfan did not affect the parasite activity. Institute Publication No 1030.  相似文献   

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